DESCRIPTION

The function tnfctl_register_funcs() is used to store client-specific data on a per-probe basis. It registers a creator and a destructor function with hndl,
either of which can be NULL. The creator function is called for every probe that currently exists in hndl. Every time a new probe is discovered,
that is brought in by dlopen(3DL), create_func is called.

The return value of the creator function is stored as part of the probe state and can be retrieved by tnfctl_probe_state_get(3TNF) in the member field client_registered_data.

destroy_func is called for every probe handle that is freed. This does not necessarily happen at the time dlclose(3DL) frees the shared object. The probe handles are freed only when hndl is closed by tnfctl_close(3TNF). If tnfctl_register_funcs() is called a second time for the same hndl,
then the previously registered destructor function is called first for all of the probes.